problem with the spectrum analyser in rotation case

[ings]

so in my case when i have this value
V=1r/s
alpha=2*pi*V*t
alpha=[0,360degree]
i will put the value of sweep time equal to t=1s
but the spectrum analyser will store the value of receiving power each 1s and for example for t=0-->alpha=0 i will save the first detection value

 

[D.A.(Tony)Stewart]

You can pseudo sync by luck and single sweep to get 2 rotations.

Or you can create an index marker to trigger SA with signal from Hall sensor from slot or key in shaft or use black Sharpy Pen line on shiny metal surface of rotor using optical reflection at 3mm using 5mm IR LED and IR photo diode or logic output. Both parts need a black tunnel or heat shrink to focus beam at 30 deg between emitter/detector in some block of material rigidly mounted and pointing at surface of rotating shaft.

Distance affects quality greatly and load R is set for dark current to one logic level. 5V schmitt input gates work well with 10mA on IR emitter and maybe 10k ~100k on photo diode to sense no current from reflected black level stripe. If you shop around you can buy for $10 or DIY for $1 make stripe = 2-3mm wide.

then output analog or logic pulse to SA trigger. And adjust sweep for slightly more than 1 rotation like 400 deg= 10 divisions or if you prefer 36 deg/div. or if 8 div... You get the idea...use R to control gain to get full swing.

- - - Updated - - -

You can even use RED LEDs for both with 100k on LED reverse biased at 5v max as a photo detector., but inferior fluorescent flicker rejection.

 

[ings]

so i need an ir emiiter ans a photo diode to find the result exactly

 

[D.A.(Tony)Stewart]

To be precise on start of sweep , yes. Properly indexed at lowest signal direction. So front rear peaks are centred.


Emitter .. Any remote control, detector any , but must have black plastic daylight blocking filter. Like old VCR or integrated into Sharp/Vishay part.

export data into XLS for RADAR plots

 

[volker@muehlhaus]

i will put the value of sweep time equal to t=1s
but the spectrum analyser will store the value of receiving power each 1s and for example for t=0-->alpha=0 i will save the first detection value

No.

No.

The spectrum analyzer - analog or digital - will show many different time samples. Not only one value at 1s. You will see the complete curve from t=0s to t=1s, with the change of received power over time. This is really simple and will easily solve your problem. Depending on the time scale, you will see different number of rotations. And as explained, maximum is where polarization is in the same plane and minimum is where polarization is 90° different. It should be very easy to see, with no need for angle sensors.

 

[D.A.(Tony)Stewart]

What RPM or Hz?

Adjust full time sweep to capture 1 cycle, thats all!

 

[ings]

What RPM or Hz?

Adjust full time sweep to capture 1 cycle, thats all!

but you saaid that the sweep time must have the same value to the antenna rotation period

 

[FvM]

"Cycle" or "rotational period" refers to the same thing. Apparently 1 s in your case.

V=1r/s

 

[ings]

plz i m fixed the sweep value 1s
and i receive this value of the received power in my sspectrum analyser
-47,-30 -19dBm..
and i chosse the max value in 30° and the mni value in 180°
but it is not necessary that my curve is lineairry because when the value of rotation velocity is bigger the variation of the received power is bigger